added gloabl metadata parsing
Fix loadGlobalMetadata on Windows
Fix root directory in directory-wise metadata and beautify code
Track metadata dependencies

I had to prepend some Rules to global Rules set. This might be possible
to replaced by a correct Store.set call.
I also had to prepend some Compile rules.
Added test case for global metadata
set internalRules last, so that it can be overrided by rules
Unified code for global and external metadata

Didn't clean up unused code though
Merge pull request #190 from krsch/master

Implemented per-directory metadata support